Six things to mess up your wifi
people are bags of water is one
http://news.yahoo.com/s/pcworld/20110517/tc_pcworld/sixthingsthatblockyourwifiandhowtofixthem;_ylt=AmlfiMd9oh6_nPyNJj9uhABk24cA;_ylu=X3oDMTQwbGZvY2VrBGFzc2V0A3Bjd29ybGQvMjAxMTA1MTcvc2l4dGhpbmdzdGhhdGJsb2NreW91cndpZmlhbmRob3d0b2ZpeHRoZW0EY2NvZGUDb2ZmcHpmMzSorry about the really long url but I don't know how to shorten it.
The article it links to points out six things you can do to improve your wifi connection up to and including security. It also (laughs a little) says people or rather the human body because it is made up of mostly water anyway can interfere if too many gather in one place at a time. I thought it worth the read.